A seawater bacterium, designated IMCC3195T, was isolated from the Antarctic coast. Cells of the novel strain were Gram-negative, rusty-coloured, strictly aerobic, chemoheterotrophic, non-budding and non-motile rods or vibrioids that possessed a thin prostheca. Based on 16S rRNA gene sequence comparisons, the novel strain was most closely related to the genera Hyphomonas (89.4-90.9%), Maricaulis (90.1-90.4%), Hirschia (89.0%) and Oceanicaulis (87.9%) of the family Hyphomonadaceae. Phylogenetic analyses also showed the Antarctic isolate to be only distantly related to the genera of stalked bacteria of marine origin in the family Hyphomonadaceae. The DNA G+C content of the novel strain was 60.3 mol% and the predominant cellular fatty acids were C18:1omega7c (41.9%), C17:1omega8c (21.4%) and C17:0 (14.3%). The major quinone was Q-10. Several phenotypic and chemotaxonomic characteristics, including optimum temperature and salinity range for growth, cell morphology, pigmentation and fatty acid content, differentiated the novel strain from other related genera in the family Hyphomonadaceae. From the taxonomic evidence collected in this study, it is suggested that strain IMCC3195T (=KCCM 42687T=NBRC 103098T) represents a new genus and novel species in the family Hyphomonadaceae, for which the name Robiginitomaculum antarcticum gen. nov., sp. nov. is proposed.